U.S. patent number 4,994,146 [Application Number 07/263,926] was granted by the patent office on 1991-02-19 for creping adhesive utilizing polymer-polymer complex formation.
This patent grant is currently assigned to Kimberly-Clark Corporation. Invention is credited to Dave A. Soerens.
United States Patent |
4,994,146 |
Soerens |
February 19, 1991 |
Creping adhesive utilizing polymer-polymer complex formation
Abstract
In the manufacture of creped tissue products, the adhesion
between the tissue sheet and the creping cylinder can be increased
by applying one component of an adhesive complex to the sheet and
another component of an adhesive complex to the creping cylinder.
When the two components are brought into contact at the pressure
roll nip, an adhesive complex is formed which adheres the sheet to
the creping cylinder.
Inventors: |
Soerens; Dave A. (Neenah,
WI) |
Assignee: |
Kimberly-Clark Corporation
(Neenah, WI)
|
Family
ID: |
23003837 |
Appl.
No.: |
07/263,926 |
Filed: |
October 28, 1988 |
Current U.S.
Class: |
162/112;
162/164.6; 162/168.1; 162/184 |
Current CPC
Class: |
D21H
17/43 (20130101); D21H 17/53 (20130101); D21H
17/55 (20130101); D21H 21/146 (20130101); D21H
25/005 (20130101) |
Current International
Class: |
D21H
17/00 (20060101); D21H 25/00 (20060101); D21H
17/53 (20060101); D21H 17/43 (20060101); D21H
17/55 (20060101); D21H 21/14 (20060101); D21H
025/04 () |
Field of
Search: |
;162/111,112,168.1,164.6,164.1,184 ;264/283 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Chin; Peter
Attorney, Agent or Firm: Croft; Gregory E.
Claims
I claim:
1. In a method for making creped tissue wherein a tissue web is
adhered to a creping cylinder and dislodged therefrom with a doctor
blade, the improvement comprising adhering the web to the creping
cylinder with an adhesive complex wherein a first water-soluble
component of the adhesive complex is applied to the surface of the
creping cylinder and a second water-soluble component of the
adhesive complex is applied to the surface of the web such that the
adhesive complex is formed when the web is brought into contact
with the creping cylinder, said first component comprising a
polyacid selected from the group consisting of polyacrylic acid,
polymethacrylic acid, ethylene maleic acid copolymer, ethylene
acrylic acid copolymer, ethylene methacrylic acid copolymer,
styrene maleic acid copolymer, and mixtures thereof and said second
component being selected from the group consisting of a polyether,
a polyamide, and mixtures thereof.
2. The method of claim 1 wherein the polyacid is a mixture of
polyvinyl alcohol and polyacrylic acid.
3. The method of claim 1 wherein the polyacid is a mixture of
polyvinyl alcohol and polymethacrylic acid.
4. The method of claim 1 wherein the polyacid comprises methyl
vinyl ether-maleic acid copolymer.
5. The method of claim 1 wherein the polyacid comprises polyacrylic
acid.
6. The method of claim 1 wherein the polyacid comprises
polymethacrylic acid.
7. The method of claim 1 wherein the polyether is (poly) ethylene
oxide.
8. The method of claim 1 wherein the polyether is (poly)propylene
oxide.
9. The method of claim 1 wherein the polyether is ethylene
oxide/propylene oxide copolymer.
10. The method of claim 1 wherein the polyether is
(poly)tetramethylene oxide.
11. The method of claim 1 wherein the polyether is poly vinyl
methyl ether.
12. The method of claim 1 wherein the polyamide is (poly)
vinylpyrrolidone.
13. The method of claim 1 wherein the polyamide is (poly)ethyl
oxazoline.
14. The method of claim 1 wherein the polyamide is
(poly)amidoamine.
15. The method of claim 1 wherein the polyamide is
(poly)acrylamide.
16. The method of claim 1 wherein the polyamide is polyethylene
imine.
17. The method of claim 1 wherein the polyacid is a mixture of
polyvinyl alcohol and polyacrylic acid and wherein said second
component is (poly) ethyl oxazoline.
18. The method of claim 1 wherein the polyacid is a mixture of
polyvinyl alcohol and polyacrylic acid and wherein said second
component is (poly)ethylene oxide.
19. The method of claim 1 wherein the polyacid is a mixture of
polyvinyl alcohol and poly methacrylic acid and wherein said second
component is (poly)ethyl oxazoline.
20. The method of claim 1 wherein the polyacid is a mixture of
polyvinyl alcohol and polymethacrylic acid and wherein said second
component is (poly)ethylene oxide.
Description
BACKGROUND OF THE INVENTION
In the manufacture of tissue products and the like in which a wet
laid fibrous web is dewatered, dried, and creped, it is common
practice to apply a creping adhesive to the surface of the creping
cylinder (such as a Yankee dryer) at a point just prior to pressing
the web against the cylinder surface. For example, U.S. Pat. No.
4,684,439 to Soerens teaches creping adhesives containing polyvinyl
alcohol and the reaction product of a polyalkylene polyamine, a
saturated aliphatic dibasic carboxylic acid, and a
poly(oxyethylene) diamine. U.S. Pat. No. 4,528,316 to Soerens and
U.S. Pat. No. 4,501,640 to Soerens teach creping adhesives
containing polyvinyl alcohol and cationic polyamide resins. U.S.
Pat. No. 4,440,898 to Pomplun et al. teaches creping adhesives
containing ethylene oxide/propylene oxide copolymers. U.S. Pat. No.
4,436,867 to Pomplun et al. teaches creping adhesives containing
poly 2-ethyl-2-oxazoline and a high molecular weight thermoplastic
polymer. In addition it has been disclosed to apply the creping
adhesive at more than one location. See, for example, U.S. Pat. No.
4,064,213 to Lazorisak et al.
The chemical literature has reported polymer complex formulation
between water-soluble polymers (see K. L. Smith, et al., Industrial
and Engineering Chemistry, 51 (11), 1361, (1959); Y. Osada, Journal
of Polymer Science: Polymer Chemistry Edition, 17, 3485, (1979); S.
K. Chatterjee, et al., Die Angewandte Makromolekulare Chemie, 116,
99, (1983)). These complexes generally form as a result of very
specific and very stable hydrogen bonds formed when the polymers
make contact in solution. Complex formation is indicated by an
increase in the viscosity of the combined solutions or the
formation of a water-insoluble precipitate when solutions of the
two polymers are combined. In particular, poly acids such as
(poly)acrylic acid or (poly)methacrylic acid are reported to form
complexes with poly ethers such as (poly)ethylene oxide and poly
amides such as (poly)vinylpyrrolidone or (poly)ethyl oxazoline.
However, there is no suggestion in these references that the
polymer complexes can be created in situ during the creping of
tissue.
SUMMARY OF THE INVENTION
It has now been discovered that the adhesion of a paper web to a
creping cylinder (such as a Yankee dryer) can be enhanced by
adhering the paper web to the creping cylinder with a
polymer-polymer adhesive complex formed from at least two
separately applied water-soluble polymeric components. One
water-soluble polymeric component is applied to the creping
cylinder and the other water-soluble polymeric component is applied
to the paper web. When the paper web contacts the creping cylinder,
as at the pressure roll nip, the adhesive complex is formed and
adhesion of the web to the creping cylinder is achieved. Improved
uniformity and control of creping is believed to result because, in
contrast to conventional creping adhesives, both surfaces bonded
together at the pressure roll nip are treated with water-soluble
polymeric components having an affinity for the surface to which
they are applied. Changes in adhesion due to variation in furnish
or wet-end chemicals should be reduced.
In addition, in typical creping operations the adhesion of the web
to the Yankee dryer is known to be strongly affected by drying
conditions as a natural consequence of using water-soluble creping
adhesives. The alternative of using water-insoluble creping
adhesives is not feasible because of problems associated with
contamination of the felt and/or fabric. However, this invention
can combine the advantages of both water-soluble and
water-insoluble creping aids because the water-soluble polymeric
components which form the adhesive complex remain water-soluble
until they come into contact with each other at the pressure roll
nip and form the adhesive complex. Therefore the adhesive bond
itself is less water-sensitive while the materials used to form the
adhesive bond remain water-soluble and thus minimize fabric/felt
contamination problems.
Hence, in one aspect the invention resides in an improved method
for making creped tissue wherein a tissue web is adhered to a
creping cylinder and dislodged therefrom with a doctor blade, the
improvement comprising adhering the web to the creping cylinder
with an adhesive complex wherein a water-soluble polymeric
component of the adhesive complex is applied to the surface of the
creping cylinder and another water-soluble polymeric component of
the adhesive complex is applied to the surface of the web such that
the adhesive complex is formed when the web is brought into contact
with the creping cylinder.
For purposes herein, "water-soluble" means that the polymers
dissolve completely in water to give a true solution as opposed to
a latex or suspension of undissolved particles.
In order for the adhesive complex to function effectively, it is
necessary that the water-soluble polymeric component applied to the
creping cylinder surface have an affinity for that surface.
Likewise, the water-soluble polymeric component applied to the
paper web must have an affinity for the fibers making up the web.
Otherwise the web will not be adequately adhered to the creping
cylinder.
The water-soluble polymeric component applied to the creping
cylinder surface preferably is an aqueous solution of a polyacid or
a mixture of a polyacid and another water-soluble polymer. Suitable
polyacids include polyacrylic acid ("PAA"), polymethacrylic acid,
methyl vinyl ether-maleic acid copolymer, ethylene maleic acid
copolymer, ethylene acrylic acid copolymer, ethylene methacrylic
acid copolymer, styrene maleic acid copolymer, and the like. Number
average molecular weights for these components should be from about
10,000 to about 500,000.
The water-soluble polymeric component applied to the web is
preferably an aqueous solution of a polyether, a polyamide, or a
mixture of one or both with another water-soluble polymer. Suitable
polyethers include (poly)ethylene oxide ("POLYOX"), (poly)propylene
oxide, ethylene oxide/propylene oxide copolymers, (poly)tetra
methylene oxide, poly vinyl methyl ether, and the like. Suitable
polyamides include (poly)vinylpyrrolidone, (poly)ethyl oxazoline
("PEOX"), (poly)amidoamine, (poly)acrylamide, polyethylene imine,
and the like. Number average molecular weights for these components
should be from about 10,000 to about 500,000.
Other water-soluble polymers which can be mixed with either of the
water-soluble polymeric components used to form the adhesive
complex include polyvinyl alcohol (PVA), carboxyl methyl cellulose,
hydroxypropyl cellulose, and the like.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 schematically shows a typical tissue-making process and
illustrates locations suitable for separately applying the two
water-soluble polymeric components in accordance with this
invention.
DETAILED DESCRIPTION OF THE DRAWING
Directing attention to the Drawing, the invention will be described
in more detail. Represented in FIG. 1 is a schematic drawing of a
basic tissue-making process in which the practice of the method of
this invention is illustrated. Shown is a headbox 1 which serves to
deposit an aqueous slurry of papermaking fibers onto a continuous
forming fabric or wire 2. Water passes through the wire leaving a
wet fibrous web 3 on the surface of the wire. The wet web is
transferred to another continuous fabric or felt 4 which serves to
further dewater the web. It will be appreciated by those skilled in
the art that a great many variations in the tissue-making process
are possible and FIG. 1 is presented only for the purpose of
placing the method of this invention in context.
Prior to being adhered to the creping cylinder 5 or Yankee dryer,
the web is sprayed 6 with an aqueous solution of one water-soluble
polymeric component of the adhesive complex. This can be done at
any point in the process prior to the web contacting the surface of
the creping cylinder. The spray can also be directed into the nip
between the pressure roll 8 and the creping cylinder. The other
water-soluble polymeric component is applied to the surface of the
creping cylinder, as by a spray 9 as shown at the 6 o'clock
position. When the web contacts the creping cylinder in the
pressure roll nip, the adhesive complex components react to form
the adhesive complex, which adheres the web to the creping
cylinder. The web is subsequently dislodged from the creping
cylinder by a doctor blade 10, resulting in a creped web.
Webs particularly suitable for purposes of this invention include
tissues, towels, and the like which have basis weights of from
about 3 to about 40 pounds per 2880 square feet. Cellulosic webs
are preferred, but webs containing synthetic fibers can also be
used.
EXAMPLES
Example 1
Peel Adhesion
The increase in adhesion between a web and a surface achieved by
the adhesive complex in accordance with this invention was
illustrated by a laboratory test method performed as follows. A
series of cast iron plates measuring 2 inches by 5 inches by 0.25
inches thick was coated with an aqueous mixture of polyvinyl
alcohol (Elvanol 7515 manufactured by E. I. duPont, Wilmington, DE)
and polyacrylic acid (Alcosperse 404 manufactured by Alco Chemical
Corporation, Chattanooga, TN). The mixture, at 10 weight percent
solids, was applied with a rod tightly wound with #26 wire and
allowed to air dry at room temperature. Various blend ratios were
used as shown in Table 1 below. The coated cast iron plate
simulates the surface of the creping cylinder with one component of
the adhesive complex applied.
A cotton cloth was used to simulate the tissue web. The cloth was
soaked either in deionized water, as a control, or in dilute
solutions of either of two water-soluble polymers which form a
complex with polyacrylic acid, i.e. (poly)ethyloxazoline (grade 500
manufactured by Dow Chemical Corporation, Midland, MI) or
(poly)ethylene oxide (WSR-N80 manufactured by Union Carbide,
Danbury, CT). Excess moisture was squeezed from the cloth strip and
the strip was applied to the coated plate and rolled down with a 10
pound roller. The adhered sample was then placed on a hot plate and
dried until the cloth surface reached a temperature of 180.degree.
F. The sample was immediately transferred to an Instrumentors
Slip/Peel tester and the 180 degree peel adhesion was measured at
12 inches per minute. The average adhesion over a 1 inch peel
distance was recorded. The average of 5 or 6 replicates of each
combination of plate coating and soak solution are recorded in
Table 1 below.
TABLE 1
__________________________________________________________________________
Peel Adhesion (grams/2 in width) Plate Coating Composition Cloth
Soak Composition (% PAA/% PVA) (WATER) (.5% PEOX) (1% PEOX) (.5%
POLYOX)
__________________________________________________________________________
100/0 232 339 385 253 80/20 331 378 513 395 60/40 378 558 615 568
40/60 499 540 518 523 20/80 348 369 348 536
__________________________________________________________________________
As Table 1 shows, the addition of the complex-forming component to
the soak solution increases the adhesion above the water control
value in each case. Also, the magnitude of the adhesion enhancement
varies with the amount of polyacrylic acid in the plate
composition, the largest increase being observed with the 60/40
blend of PAA/PVA. For this blend a 48% increase is found with 0.5%
PEOX, a 63% increase with 1% PEOX, and a 50% increase with 0.5%
POLYOX. In general, the most favorable ratios for adhesive complex
formation would be one repeat unit of acrylic acid to one repeat
unit of the second polymer. Therefore, the best conditions will
vary with the molecular weight of each complexing component.
Example 2
Peel Adhesion
Sixty (60) grams of methyl vinyl ether-maleic anhydride copolymer
was slurried in 600 grams of water and shaken overnight to
hydrolyze it to the water-soluble di-acid form. The pH of the 10%
solution was found to be 1.94.
The 10% solution of hydrolyzed methyl vinyl ether-maleic anhydride
copolymer (Ganting AN 149 made by GAF Corporation, New York, NY)
was combined with an aqueous solution of PVA (Elvanol 75-15), also
at 10% solids, in the proportions shown in Table 2 below. These
blends were coated onto the cast iron panels. The cloth strips were
soaked in PEOX or water. The cloth strips were tested for peel
adhesive as previously described. The results are shown in Table 2
below.
TABLE 2 ______________________________________ Peel Adhesion
(grams/2 inch width) Plate Composition Cloth Soak Composition (%
PVA) (WATER) (1% PEOX) (% INCREASE)
______________________________________ 100/0 108 135 25% 80/20 133
173 30% 60/40 173 237 37% 40/60 188 261 39% 20/80 215 245 14%
______________________________________
This system again demonstrates increased adhesion as a result of
complex formation between the polyacid and the PEOX.
Example 3
Peel Adhesion (Reverse Application of Components)
In order to illustrate the effect of reversing the application of
the adhesive complex components, the above-described test procedure
was repeated with the following combinations:
(a) PEOX/PVA blends coated onto the cast iron panels and the cotton
cloth soaked in water or a solution of 1% PAA (Acrysol A-1
manufactured by Rohm and Haas Corporation, Philadelphia, PA).
(b) A blend of a cationic polyamide resin (Kymene manufactured by
Hercules, Inc., Wilmington, DE) and PVA coated onto the cast iron
panels and the cotton cloth soaked in water or a solution of 1%
PAA.
(c) A blend of PEOX and PVA coated onto the cast iron panels and
the cotton cloth soaked in water or a solution of 1% PAA. The
results are set forth in Table 3 below.
TABLE 3 ______________________________________ Peel Adhesion
(grams/2 inch width) Cloth Soak Composition (% Plate Composition
(WATER) (1% PAA) DECREASE) ______________________________________
(% PEOX/% PVA) 50/50 282 246 13% 30/70 381 267 30% 10/90 411 358
13% (% Kymene/% PVA) 184 163 11% 33/67 (% PEOX/% PVA) 243 214 12%
20/80 ______________________________________
As clearly shown in Table 3, with the polyacid applied to the cloth
the adhesion is reduced relative to the water control. This is
believed to be due to poor anchorage of the acid polymer to the
cloth. When these samples were peeled apart a white film was
present, indicating complex formation. However, because of the poor
anchorage the failure point was between the complex and the cotton
cloth.
Example 4
Continuous Production of Facial Tissue
Facial tissue was prepared by wet-laying a web of papermaking
fibers (50/50 northern softwood kraft/eucalyptus) which had been
treated with 0.25% wet strength resin (Kymene). The basis weight
was 7.5 pounds/2880 ft..sup.2. The web was dewatered and pressed
onto a Yankee dryer with a pressure roll. Prior to pressing onto
the Yankee dryer the web surface was sprayed with a dilute solution
of one of the polymeric adhesive complex forming components. The
amount applied was equivalent to either 1 or 3 pounds per ton of
dry fiber. Also, several samples were run in which no spray was
applied to the web surface. In these cases the wet strength resin
added at the wet end acts as the polymer complex forming
component.
The other component for forming the adhesive complex was applied to
the Yankee dryer at a 6 o'clock position at add-on rate of about 5
pounds/ton of dry fiber. The adhesive complex forming component was
applied to the Yankee dryer as an aqueous blend with various
amounts of polyvinyl alcohol, which provides enhanced film forming
properties on the Yankee dryer. The resulting creped tissue
products were submitted to a trained sensory panel for an
evaluation of softness. Higher sensory panel numbers correspond to
greater softness.
The combinations run and the resulting sensory panel softness
values are shown in Table 4 below.
TABLE 4 ______________________________________ Facial Tissue
Softness Dryer Surface Sheet Surface Amount Composition Composition
(pounds/ton) Softness ______________________________________
40PVA/60PAA NONE (control) -- 7.2 40PVA/60PAA POLYOX 3 7.65
40PVA/60PAA PEOX 1 7.8 40PVA/60PAA PEOX 3 8.0 8OPVA/20PMA.sup.1
NONE (control) -- 7.7 80PVA/20PMA POLYOX 1 8.15 80PVA/20PMA POLYOX
3 8.05 80PVA/20PMA PEOX 1 8.05 80PVA/20PAA NONE (control) -- 8.08
80PVA/20PAA POLYOX 3 8.2 80PVA/20PAA PEOX 3 7.85 (high strength)
40PVA/60PMA NONE (control) -- 8.1 40PVA/60PMA POLYOX 1 8.1
40PVA/60PMA PEOX 1 7.8 (high strength)
______________________________________ .sup.1 PMA = polymethacrylic
acid, prepared by the addition of sulfuric acid to Aquatreat 225
(sodium salt of polymethacrylic acid) to a pH of 2.8. Aquatreat 225
is a product of Alco Chemical, Chattanooga, TN.
The results generally confirm an increase in softness with
increasing adhesion, although there are some inconsistencies. Note
that the examples above with no addition to the sheet surface can
still have some complex formation by interaction with the wet-end
applied Kymene. Therefore these controls are not quite the same as
the laboratory controls where no complex formation was possible.
Note also that addition of PEOX to the sheet surface tended to
result in tissue samples of higher strength. This increased
strength was reflected in lower softness relative to the control
samples. If the samples were normalized to equivalent strengths,
these samples would exhibit softness values of about 8.1.
Nevertheless, the method of this invention can increase the
adhesion between the tissue sheet and the creping cylinder such as
to improve the softness of the resulting product. At the same time,
certain processing advantages can be obtained, such as more uniform
creping control.
It will be appreciated that the foregoing examples, shown for
purposes of illustration, are not to be construed as limiting the
scope of this invention, which is defined by the following
claims.
* * * * *